1. Field of the Invention
The present invention relates generally to electric motors for automotive applications, and, more particularly, to an electric motor incorporating vibration reduction and acoustic engineering principles to effectively minimize component vibration and noise generated during operation.
2. Description of the Prior Art
Fractional HP direct current electric motors are commonly used in the automotive industry to power heating, ventilation and/or air conditioning systems, radiator engine cooling fans, etc . . . . These motors generally include an outer frame or housing and an armature mounted for rotational movement within the housing. An electric current is carried through electromagnetic windings of the armature to create an electromagnetic field which cooperates with permanently fixed magnets disposed within the housing to cause rotation of the armature and consequent powering of the system.
Due to various factors such as motor or armature imbalance, unequal magnetic forces and bearing defects, operation of the motor may cause excessive surface vibration of the motor components. This vibration results in the generation of undesired airborne noise and structural sound which often propagates to the vehicle interior, thereby having a deleterious affect on passenger comfort.
Automotive manufacturers and suppliers have undertaken efforts to minimize acoustic noise radiation of electric motors. One conventional approach incorporates resilient washers which are positioned about the armature shaft proximate the bearings to resist movement of the armature relative to the frame, thus, attempting to minimize noise created by axial movement of the armature. Other noise suppression approaches include the use of noise absorption materials, barriers and circuits.
None of the foregoing efforts, however, discloses a complete solution for effective suppression of vibration and noise generated by an electric motor.